A radiation emitting apparatus includes a radiation source to generate radiation, a first collimator to define a maximum radiation field of the radiation a second collimator to regulate the radiation field and direction of irradiation a swing portion that swings in two directions orthogonal to each other a displacement detector to detect displacement of the second collimator relative to a reference point a drive mechanism to drive the swing portion a control unit to control the drive mechanism and a storage unit included in the control unit to store one or more parameters related to mechanical movement of the swing portion. The control unit generates feedforward control information based on an inputted target swing angle, a detected displacement, and the one or more parameters stored in the storage unit, and outputs a drive signal containing the feedforward control information to the drive mechanism.
